In edge emitting semiconductor lasers, at the surfaces of the side facets which form the laser mirrors of the edge emitting semiconductor laser, there is an increased probability of non-radiative recombinations occurring, that is to say that charge carriers recombine to an increased extent in the region of the side facets with generation of heat. The charge carrier depletion that occurs as a result is compensated for by absorption of laser radiation. Since the generation of heat is more intense at the side facet than in the interior of the semiconductor body, the semiconductor is warmer here, whereby the band gap of the semiconductor material is reduced. As a result, non-radiative recombinations are promoted further, which can lead to a further increase in the evolution of heat. At comparatively high laser intensities, an unstable circuit can arise which can lead as far as the melting of the side facet. This possible destruction mechanism is critical for the active layer, in particular, since the adjacent layers generally have a larger band gap and are therefore substantially transparent to the laser radiation.
The document EP 0 416 190 A1 discloses providing the side facets of the semiconductor laser with a passivation layer.
The document U.S. Pat. No. 6,323,052 B1 describes treating the side facets of the semiconductor laser by means of a sputtering process in order to eliminate oxides there that might lead to non-radiative recombinations.
U.S. Pat. No. 5,171,707 describes a method by which transparent regions are produced in the region of the side facets of an edge emitting semiconductor laser by diffusion-induced intermixing, which transparent regions do not absorb the radiation generated by the active layer. A similar method is also known from the document WO 96/11503 A2.